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Acinetobacter

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Acinetobacter is a genus of gram-negative bacteria that includes opportunistic pathogens. The most clinically important species are A. baumannii and A. lwoffii. A. baumannii is commonly found in hospitals and can cause infections in immunocompromised patients. It is able to survive on surfaces and in the environment. Treatment is challenging due to high levels of antibiotic resistance, though carbapenems and polymyxins may be used. Proper hygiene and cleaning can reduce transmission in clinical settings.

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ACINETOBACTER By Shahbaz Raza
Introduction The name, Acinetobacter, comes from the Latin word for "motionless," because they lack cilia or flagella with which to move. Have 32 species, A. baumanii and A. lwoffii have greatest clinical importance. 2
Introduction Most species are not significant sources of infection. However, one opportunistic species, Acinetobacter baumannii, is found primarily in hospitals and poses a risk to people who have supressed immunity. >2/3 of Acinetobacter infections are due to A. baumannii 3
Acinetobacter Gram-Negative Coccobacilli Strictly aerobic Nonmotile Catalase positive Oxidase negative 4
Epidemiology Environmental reservoirs Soil Fresh water Vegetables Animals Body lice, fleas, ticks 5
Epidemiology In the hospital Environmental surface Ventilators, dialysis machines, air ventilation systems, water sources Hands Contaminated suction equipment Respiratory, urinary, GI tracts & wounds of patients 6
Growth Requirment Aerobic Grow at 44属 C Differential Media MacConky Agar Selective Media CHROM Agar Leeds Acinetobacter Agar 7
8 MacConky Agar CHROM Agar Leeds Acinetobacter Agar
Biochemical Profile Both A.baumennii and A.lwofii are Catalase positive and Oxidase Negative. A.baumennii ferment glucose, xylose and lactose but A.lwofii cannot ferment. 9
Rapid Detection Rapid detection of Acinetobacter can be done by RapID ONE Panel (remel) and Api 20 E strips. These can differentiate up to species level. 10
Molecular Detection A.baumennii and A.lwofii can be detected by PCR. recA specific primers are used to detect recA gene in A.baumennii, giving a 382 bp fragment est specific primers are used to detect est gene in A.lwofii, giving a 309 bp product. 11
Pathogenesis Opportunistic pathogen Survive under dry conditions Virulence Factors Polysaccharide capsule, prevent complement activation, delay phagocytosis Fimbriae (adhere to human bronchial epithelium) Pilli (colonization of environmental surface to form biofilms) 12
Transmission Acinetobacter can be spread from person to person (infected or colonized patients), contact with contaminated surfaces of exposure to the environment. 13
Antibiotic Resistance Acinetobacter species are capable of accumulating multiple antibiotic resistance genes, leading to the development of multidrug-resistant or even panresistant strains. 14
Antibiotic Resistance Mechanisms Antibiotic-altering enzymes (beta-lactams, carbapenems, aminoglycosides) Reduced outer membrane porin expression (beta-lactams, carbapenems) Altered penicillin-binding proteins (beta- lactams, carbapenems) DNA gyrase and topoisomerase IV mutations (quinolones) 15
Treatment Multidrug-resistant A. baumannii is a common problem in many hospitals. First line treatment is with a Carbapenems antibiotic such as imipenem, but carbapenem resistance is increasingly common. Other treatment options include Polymyxin, Tigecycline and Aminoglycosides. 16
Treating the Resistant Infections Colistin and Polymyxin B have been used to treat highly resistant Acinetobacter infections. The choice of appropriate therapy is further complicated by the toxicity of colistin which is mainly renal. Acinetobacter isolates resistant to colistin and Polymyxin B have also been reported 17
Summary Opportunistic pathogen Nosocomial infection Grow best at aerobic conditions Can be transmitted by contact Possessing antibiotic resistant 18
Acinetobacter pakistanensis 19
20 Wash your hands and shut them off.

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Acinetobacter

Editor's Notes

  • #3: A. Hemolyticum A. Junnii A. Johnsonii
  • #5: Short, broad rod during rapid growth Coccobacillary shape in stationary phase
  • #9: Colonies are 1 to 2 mm, nonpigmented, domed, and muciod, with smooth to pitted surfaces.
  • #10: Oxidase negative (opposite to Neisseria spp. or Moraxella spp.) Haemolytic Indole negative. Catalase positive.
  • #16: Quinoloine and nalidixic acid- inhibit DNA/RNA synthesis Rifamycine- prevent DNA synthesis Erythromycine, chloramphenicol- disruption of 50s subunit of ribosome Tetracycline, gentamycine and streptomycine- 30s subunit disruption
  • #17: Polymyxin- Disruption of cell membrane Penicilline, cephalosporine and beta-lactam - inhibition of cell wall synthesis Sulfonamide and trimethoporine- inhibition of folic acid synthesis